The get field mapping API can be used to get the mapping of multiple fields from more than one index or type
with a single call. General usage of the API follows the
following syntax: host:port/{index}/{type}/_mapping/field/{field} where
{index}, {type} and {field} can stand for comma-separated list of names or wild cards. To
get mappings for all indices you can use _all for {index}. The
following are some examples:

GET /twitter,kimchy/_mapping/field/message
GET /_all/_mapping/tweet,book/field/message,user.id
GET /_all/_mapping/tw*/field/*.id